1. Field of Invention
This invention relates to aqueous liquid combined conversion coating and lubricant coating compositions and to uses thereof. These compositions, in a single liquid-coating-forming contact with a metal substrate followed by drying into place on the metal substrate surface, produce a coating that combines both a solid adherent conversion coating and a solid and/or liquid lubricant and is highly effective in facilitating cold working of the thus-coated metal substrate in any type of cold working operation that requires deformation of the thus-coated surface of the object by relative motion between this coated substrate surface and a forming tool such as a drawing die.
2. Background Art
Many aqueous liquid compositions that form coatings on metal surfaces that protect the metal surface while it is being cold worked are known. The previously most effective ones have generally been zinc, calcium, and/or sodium soaps applied over a preceding heavy phosphate conversion coating on steel substrates or over a complex calcium aluminate conversion coating on aluminum substrates. (Normally, a sodium stearate or other sodium soap salt is applied over a zinc phosphate coating or a calcium aluminate coating. Reaction between the sodium soap and the zinc or calcium in the previous conversion coating is believed to result in both zinc or calcium soap and sodium soap layers, and this type of lubricant is accordingly often called a “reactive” lubricant.) However, this combination is environmentally disadvantageous, especially when used over phosphate coatings, because the liquid compositions used to form phosphate coatings generally contain some types of metal ions, such as those of zinc, nickel, manganese, and/or the like, that are regarded as polluting. Zinc and calcium soaps are substantially insoluble in water, but cause workplace nuisances at best and hazards at worst because they tend to form fine dust particles in the air around sites of cold working processes when used as cold working lubricants. This combination is also economically disadvantageous because it normally requires separate conversion coating and lubricant coating process steps, with associated requirements for equipment for large scale practice of cold working using this method of lubricating the metal substrates being worked.
Various polymer based lubricants have been taught in the art as replacements for the combination of stearates over zinc phosphate conversion coatings, but heretofore none of the polymer based lubricants have proved to be commercially acceptable in all applications. A frequently objectionable feature of commercial use of prior polymeric lubricants is the presence of scratches on the surface of the cold worked article.
Previous attempts to combine the best features of conversion coatings and other lubricants in a single step resulted in the issuance of U.S. Pat. Nos. 4,289,546 and 4,289,547, which have many disclosures in common, and in earlier patents cited in these two patents. In long term practice, the teachings of all of these patents proved to be commercially unacceptable for use on steel, which is the most common substrate treated for protection during cold working, because iron cations dissolved from the steel eventually accumulated in the working compositions to such an extent as to make their continued use unsatisfactory.
A major object of this invention is to provide lubricants and processes that will eliminate or at least reduce the environmental and other disutilities noted above while still achieving cold working performance that is adequate when compared with the prior art use of phosphate conversion coatings followed by zinc soap application. Other alternative or concurrent objects are to reduce total energy and/or other costs of cold forming operations, particularly by reducing process related waste of objects being cold worked, more particularly because of rejection for scratched surfaces, and/or by achieving higher production rates per unit time. Still another alternative or concurrent object is to provide a lubricant satisfactory for extruding under the more severe conditions in current commercial practice.
Except in the claims and the operating examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word “about” in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred. Also, throughout this description, unless expressly stated to the contrary percent, “parts of”, and ratio values are by weight; the term “polymer” includes “oligomer”, “copolymer”, “terpolymer”, and the like; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description or of generation in situ by chemical reactions specified in the description, and does not necessarily preclude other chemical interactions among the constituents of a mixture once mixed; specification of materials in ionic form additionally implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole (any counterions thus implicitly specified should preferably be selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, except for avoiding counterions that act adversely to the objects of the invention); and the term “mole” and its grammatical variations may be applied to elemental, ionic, and any other chemical species defined by number and type of atoms present, as well as to compounds with well defined molecules.